1. Field of the Invention
This invention relates to a computer controlled intelligent downhole safety valve system. More particularly, the invention relates to a preferably electrically but possibly hydraulically, mechanically, electromechanically, electrohydraulically or pneumatically actuated and operated system comprising a safety valve and a plurality of sensors delivering information to and receiving instructions from a processor whether located locally or remotely from the valve.
2. Prior Art
Safety valves have been in existence for some time and have consistently been important to the safety of the environment and hydrocarbon drilling and production personnel.
Traditionally, safety valves have been hydraulically actuated and were operated from the surface based upon information gleaned from the production fluid or based upon dangerous conditions at the surface.
Hydraulically actuated safety valves commonly employ a flapper valve and a flow tube movable axially relative to the flapper valve. Thus, when the tube moves downhole the flapper is pushed open and the tube connects with more production tube downhole. As long as the flow tube remains in this downhole position the flapper stays open. The flow tube is biased however to an uphole position by a relatively high rate coil spring, the urging of which is overcome by hydraulic fluid pressure exerted from a reservoir, usually located at the surface. Necessarily there is a high pressure hydraulic fluid line extending from the reservoir to the valve which may be, for example, six thousand feet below the surface. Due to the large volume of hydraulic fluid that must be moved uphole in this fluid line, closing of the flapper is not as speedy as might be desired. Moreover, safety valves of this type, as stated above, are actuated only when conditions requiring a shut-in are perceptible at the surface.
More recently some work has been done to employ electric power to actuate and control safety valves. U.S. Pat. No. 5,070,944 to Hopper discloses a downhole electrically operated safety valve comprising an electric motor which drives a gear assembly having a drive gear and an operating gear, said gears providing a ratio of 30:1. The gears are operatively connected to a two-part drive sleeve the parts of which rotate together but are capable of relative axial movement. An actuating sleeve is also employed and a solenoid operated releasable lock prevents relative axial movement between the two parts of the drive sleeve.
Even with what may be considered more advanced electrically actuated downhole safety valves, the decision making is made at the surface depending upon information obtained at the surface. This limits the effectiveness of the safety valve because whatever condition indicates to the operator, from evaluation of production fluids, that the valve should close is a condition occurring through perhaps six thousand feet of pipe before the valve is shut. Therefore, there is a significant need for a system capable of obtaining information and rendering decisions downhole as well as being capable of communicating with other downhole tools, the surface and other wells. An example of a computer controlled safety valve and production well control system is disclosed in application Ser. No. 08/599,324 filed Feb. 9, 1996, all of the contents of which are incorporated herein by reference thereto.